import java.util.ArrayList;
import java.util.HashSet;
import java.util.List;

public class Test1 {
    public static void main(String[] args) {
        HashSet<Integer> set = new HashSet<>();
        String a = "123" ;
        System.out.println(a.substring(0, 0));
       List<Integer> list = new ArrayList<>();

    }
}
